Natural lighting of the urban visual scene. Static and dynamic analysis in Barcelona.

This study stems from the collaboration with the Escola Tècnica Superior d'Arquitectura de Barcelona and concerns the evaluation of daylight in a series of public squares in the Catalan city. The work presented itself as a concrete opportunity to test and develop a new software, which allows to obtain data on luminance, spatial contrast and RGB values of the visual scene: these outputs are extrapolated from photographic images taken with different levels of exposure, thus resorting to HDR processing. Through this type of analysis it was possible to verify the relationship between the spatial and material composition of the public space, the environment lighting and the visual perception of the user. The public spaces have been examined in two different ways: one static and the other dynamic. Firstly, an analysis of the facades surrounding the squares is dealt with; after taking pictures on site at three different times of the day, every visual scene is divided into three different areas (pavement, facade, sky), obtaining with the software the corresponding luminance values and comparing them with the compositional data of the space: in this way it is possible to reflect on the design choices made in terms of composition, finishes and orientation of the elevations. The second analysis, instead, aims to assess the impact of natural lighting in the case of movement towards an urban spatial envelope. The study was carried out by comparing four progressive visual scenes placed at a distance of five meters; the software processes a grayscale image for every photo where each tonality corresponds to a precise preset luminance range: this makes it possible to evaluate the linearity of light transition between the access and the open space, and therefore the conditions of visual adaptation.